Question

an atom that contains six protons
must have a mass number of 12
must be a carbon atom
must have six neutrons
must have six electrons
has a mass of 12.01

Explanation:

The atomic number is determined by the number of protons. Carbon has an atomic number of 6, so an atom with six protons must be a carbon atom. Mass - number is the sum of protons and neutrons and can vary (isotopes), and the number of neutrons and electrons isn't always equal to the number of protons without more context about the atom's charge and isotope.

Answer:

B. must be a carbon atom